Fig. 1. Notch represses Twist expression. Lateral views of embryos stained with anti-Twist. (A,C,E,G) Whole-mount embryos. In this and all the following figures, the black bracket denotes the mesodermal segments shown at higher magnification in (B,D,F,H). (B,D,F,H) Corresponding close-ups of each embryo in (A,C,E,G). In this and all the following figures, the white bracket demarcates one mesodermal segment. (A,B) Wild-type (wt) stage 9 embryo expresses Twist at high levels uniformly throughout its mesoderm. (C,D) Wt stage 10 embryo exhibits a modulated Twist pattern along its anterior-posterior axis. Each segment consists of a low and high Twist domain. (E,F) N^null stage 10 embryo maintains high Twist expression throughout its mesoderm. Rather than modulating Twist levels, N^null mutants display uniform high Twist expression pattern characteristic of wt stage 9 embryos. (G,H) UAS-N^intra stage 10 embryo has fewer high Twist expressing cells than wt.